1. Field of the Invention
The present invention relates generally to the material composition of the blocker doors of a thrust reverser and, more particularly, to a syntactic film for protecting composite material layers of the blocker doors.
2. Description of the Prior Art
It is common practice in many commercial and military jet aircraft to brake the aircraft upon landing by effectively reversing the direction of thrust of the jet engines. A common arrangement for providing such thrust reversal is to provide a pair of clam shell shaped blocker door members pivoted within the engine housing to swing from a position eclipsing openings in the engine housing to a position intercepting the thrust gases normally passing rearwardly of the engine thereby directing the gases out of the openings. Simultaneously with the swinging movement of the clam shell doors, partitions normally covering the housing openings swing outwardly and serve as a deflection or baffle wall for further guiding the outwardly deflected thrust gases forwardly thus providing the desired reverse thrust action.
Aircraft engine thrust reversers are considered by many people to be essential to the overall operational safety of today's faster more efficient airplanes. Their use makes landings safer by minimizing the number of occurrences of overruns due to long touch downs or wet or icy runways and by providing improved directional control. In addition, they are available for use in case of an aborted takeoff to assist in stopping the aircraft. However, thrust reversers add weight, complexity and cost to an aircraft.
The evolutionary development of thrust reverser design logically included the use of metals that were able to withstand the high exhaust gas temperatures produced by earlier low bypass ratio turbofan and turbojet aircraft engines. While the use of steel and titanium was essential to the early development of thrust reversers, much undesirable weight and cost accompanied the fabrication of a highly contoured highly loaded metal structure. More recently, the need to comply with Federal noise regulations has spawned a newer generation of commercial turbofan engines with moderate to high bypass ratios, in the range of 3.0 to 6.0, and has reintroduced the use of forced mixing devices. Forced mixing of the engine bypass and core exhaust flows before exiting the jet pipe produces a more uniform velocity profile over the combined exhaust area, thus reducing noise-producing shear between the exhaust flow and ambient air. Two additional benefits typically accrue; a small increase in overall engine performance and reduced peak exhaust temperatures. The lower exhaust temperatures of the newer engines permits the use of low density and potentially lower cost, high temperature, reinforced composite materials for fabrication of the thrust reverser.